1. Field of the Invention
The present invention relates to a recording and/or reproducing apparatus, more particularly, to an imaging apparatus or a video camera system having a function of avoiding fluctuations or vibrations of pictures contained in video signals.
2. Description of the Related Art
In recent years, with video cameras integrated with a VTR coming into extensive use, their size and weight have been reduced and higher magnifications have been achieved. However, when such a video camera is used by being held by an operator's hands, vibrations of the camera may occur. Thus, it becomes necessary to compensate such vibrations. For this purpose, there have been proposed some techniques such as an inertial pendulum mechanism for preventing vibrations with a compensation optical system supported movably by a gimbals mechanism in which vibrations of pictures due to vibrations of operator's hands are compensated by the inertia of the compensation optical system; a vibration preventing system with a varying angle prism disposed in front of a front video lens wherein the apical angle of the prism is controlled in response to the output of a sensor which detects vibrations; and an electronic system for preventing vibrations wherein a video signal output from an image sensing device is stored in an image memory and picture vibrations are compensated by shifting the read-out addresses of the image memory depending on the amount of movement of the picture detected based on the information associated with the video signal stored in the image memory.
Of these techniques, the electronic system for preventing vibrations has in particular received much attention in recent years because of its advantages in that it does not need any special mechanical parts for compensating picture vibrations, and in that it is possible to reduce the size, weight, and cost due to the fact that the rapid progress of semiconductor technology permits a very large scale electronic circuit to be contained in a very small package.
FIG. 1 is a block diagram showing a configuration of a VTR incorporated with a video camera in a single device, which has a conventional electronic vibration compensation system.
In this figure, a signal is provided by a camera image sensing device 100 to a video camera signal processor 110, which performs AGC processing, gamma correction, matrix processing, and other required processing on the signal provided by the image sensing device 100. The resulting signal is output as a television image signal. This television image signal is applied to a picture vibration compensation circuit 120, which eliminates a picture vibration component included in the video signal. Then, after processing by a recording signal processor 130, the video signal is recorded on a recording tape via a recording head 140.
However, in the above-mentioned conventional VTR incorporated with a video camera in a single device having a hand-vibration compensation system, picture vibration compensation is performed on the video signal provided by the camera signal processor 110, and then the video signal is recorded with the VTR. In such an arrangement, if accurate detection is not made whether picture movement is due to hand-vibrations or due to the operator's intentional movement such as panning and tilting, then the picture vibration compensation causes the video signal to become unnatural. In an electronic picture compensation system of this type in which picture vibration is compensated based on an input video signal, interpolation is usually performed by means of electronic zooming so as to recover the reduction in the angle of view. Due to the principle of this system, degradation of resolution of the video signal occurs. Therefore, if the picture vibration compensation processing is always in operation, then the resolution of the recorded video signal is degraded even in the case where hand-vibrations do not occur.
Furthermore, the area associated with vibration compensation is automatically determined by an imaging sensing device, memory, picture quality, and the like. Therefore, if the compensation amount for vibrations exceeds the limitations, further compensation is impossible and thus the picture becomes ugly.
Furthermore, because the magnitude of motions such as hand vibrations is detected from the video signal output from the image sensing device, it is essentially difficult to make an accurate decision whether the vibrations in the video signal are due to vibrations of the hands or due to movement of an object itself. To solve this problem, some known techniques include additional electrical or mechanical vibration vector detection means such as angular velocity detection means for detecting a vibration vector. In this technique, the vibration detection means is directly attached to the body of a camera itself, and thus it is possible to decide whether the camera itself is vibrating or whether an object is vibrating. However, such an arrangement causes an increase in the complexity of the circuits and an increase in cost.